Chronic Renal Failure

Question 1

What glomerular changes occur in CRF?

Answer 1

Loss of nephrons
Remaining nephrons initially hypertrophy, leading to glomerular hyperfiltration
This results in a loss of functional reserve (GFR cannot be increased if required) and glomerular hypertension (causing further damage and glomerulosclerosis)

Question 2

List the 4 most common causes of CRF

Answer 2

Diabetes
Hypertension (can also be a symptom of CRF)
Chronic glomerulonephritis
Cystic disease

Question 3

What is uraemia?

Answer 3

Accumulation of uraemic toxins (mostly urea)

Question 4

When is uraemia symptomatic?

Answer 4

With <30% normal renal function

Question 5

What are the symptoms of uraemia?

Answer 5

Fatigue
Loss of appetite
Skin pigmentation (lemon)

Question 6

What is the specific gravity of urine in CRF? Why?

Answer 6

1.01, same as plasma

Due to lost ability to dilute or concentrate urine

Question 7

What is the different in presentation between predominant glomerular disease CRF and predominant tubular disease CRF?

Answer 7

Glomerular: Na+ retention causing hypertension
Tubular: Na+ wasting causing hypotension, impaired concentrating ability and polyuria

Question 8

What happens to [K+], pH, [Ca2+], [PO4-], vitamin D3 and PTH in CRF?

Answer 8

[K+] tends to rise, esp in late-stage (except in diabetes where it may be elevated throughout)
pH falls due to H+ retention and inability to produce ammonia (there is therefore low HCO3-)
[Ca2+] is reduced due to reduced PO4- excretion
PO4- excretion is reduced, causing an increase in [PO4-]
Vitamin D3 is reduced due to failure of activation in the kidney (contributes to hyperphosphataemia and causes renal rickets)
PTH is high due to secondary hyperPTH

Question 9

Summarise the changes in CRF

Answer 9

Specific gravity 1.01 (same as plasma)
High [K+]
Low pH
Low HCO3-
Low vitamin D3
High PO4-
High PTH
Low or normal Ca2+

Question 10

What is classified as “significant CRF”?

Answer 10

GFR <50mL/min

Question 11

Is CRF reversible?

Answer 11

No

Question 12

What demographics are pre-disposed to ARF?

Answer 12

Pre-existing renal disease

>60y.o.

Question 13

What changes can be made by the patient to benefit their remaining nephrons in CRF?

Answer 13

Low protein diet

Keeping BP low (treating hypertension)

Question 14

Define CRF

Answer 14

Urine flow <500mL/day occuring over months to years